Background Information for Enols and Enolates
An enol contains a OH attached to a C=C. An enolate ion is a structure in which a O- is next to C=C or C=O is next to C-. Tautomerize is moving an electron pair to form another double bond, along with the movement of a H. Alpha substitution is replacement of H on alpha carbon, which is C next to C=O. Carbonyl condensation is a reaction in which the electrophile is another carbonyl compound.
Halogenation of Carbonyl Compounds
Ketones and aldehydes are halogenated on the α-carbon in the presence of acid to form α-halo ketones and aldehydes. Ketones and aldehydes are halogenated on the α-carbon in the presence of base to form α-halo ketones and aldehydes. In the presence of excess base and excess halogen, methyl ketones form carboxylate anions and haloforms in the haloform reaction. In the Hell-Volhard-Zelinsky reaction, carboxylic acids are halogenated with phosphorus trihalides to yield α-halo carboxylic acids.
Alkylation of Carbonyl Compounds
Ketones and aldehydes can be treated with lithium diisopropylamide (LDA), followed by an alkyl halide, to yield α-alkyl ketones and aldehydes. Ketones and aldehydes are reacted with a secondary amine and an alkyl halide, followed by acidification to yield α-alkyl ketones and aldehydes.
Condensation of Carbonyl Compounds
Ketones and aldehydes undergo aldol condensation, in the presence of base, to form β-hydroxy aldehydes and ketones (aldols), which lose water to form α,β-unsaturated aldehydes and ketones. Esters condense in the presence of base, followed by hydrolysis, to yield β-ketoesters.
Alkylation of Dicarbonyl Compounds
Diethyl malonate is reacted with base, alkylated, then hydrolyzed to yield a substituted acetic acid, carbon dioxide, and ethanol. Ethyl acetoacetate is treated with base, alkylated, then hydrolyzed to yield a substituted acetone, carbon dioxide, and ethanol.
